Eight players are selected for the Home Run Derby and compete in a traditional playoff system where the players with the most home runs advance to the next round. Each player gets ten "outs" per round, where an out is defined as any swing that is not a home run in this case. Should a tie exist between players at the end of any round, the number of regular-season home runs by the All-Star break is the first tiebreaker and the distance of the longest home run in the first round is the second tiebreaker.

Prior to 1991, the Home Run Derby was structured as a two-inning event with each player receiving five outs per inning which allowed for the possibility of ties.

Until 2004, the Home Run Derby consisted of four American League players and four National League players. However, in 2005, Major League Baseball chose to change the look of the contest, still having eight players, but with the players representing their home countries rather than their respective leagues. This is commonly looked upon as a lead-in to the World Baseball Classic to be played in 2006. Bobby Abreu, representing Venezuela, won the First International Derby with a record 41 home runs, including a record 24 in the first round. In 2006, the Derby moved to a new format as the homerun total would be cumulative through the first two rounds. This allowed David Wright to make the final round despite only 2 homers in the second round (Wright hit 16 in the first) He eventually lost out to Ryan Howard.

Television Show

Home Run Derby was also the name of a 1959 television show held at Wrigley Field in Los Angeles pitting sluggers against each other in 9-inning home run contests. The rules were not unlike modern Home Run Derbies; however, the television show also added as an out any called strike. Nine future Hall of Famers would eventually participate in the series.

Batters were given 3 outs per inning, and the player with the most home runs after nine innings wins. If the players were tied after that time, the derby would go into extra innings as per regular baseball. The winner received $2,000 and was invited back for the next week's episode against a new opponent. The loser received $1,000.

There was extra money awarded in certain cases however. If a batter three home runs in a row, he would receive a $500 bonus. A fourth home run in a row would be worth another $500 bonus. Any consecutive home runs hit beyond that would each be worth $1,000. It is believed that Jackie Jensen was the only player to hit more than three home runs in a row (he hit 5). He still lost the contest to Mickey Mantle though.

The show was also unique in that the host, Mark Scott, would often chat with each player while his opponent was batting.

Hank Aaron held the record for most money won on Home Run Derby, winning $13,000. His run of 6 consecutive wins was ended by Wally Post, who was defeated in his next outing by Dick Stuart.

Willie Mays, who was a champion later in the run, joked with host Scott during his run that the host should be quiet while he batted and Scott took him up on it, whispering into the mic whenever Mays would step up to the plate.